Find function for Matrix

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Jonathan Moorman
Jonathan Moorman on 20 Aug 2020
Commented: Jonathan Moorman on 20 Aug 2020
Hi! I'm trying to use the find function for the first time in my code and have come across a problem. It appears that in about half my runs, the function is unable to find the value in the matrix when it is clearly there. Has anyone seen this error before or am I doing something incorrect in the code?
Below is three screenshots of the value it should be looking for (0.1573), in the matrix (a90Export6dB), and I am getting a empty vector when the value is clearly there.
Figure 1:
Figure 2:
Figure 3:

Accepted Answer

KSSV
KSSV on 20 Aug 2020
Edited: KSSV on 20 Aug 2020
When you are comapring a floating point number you should not use ==, you should fix some tolerance and use inqualitty. Check the below example code:
tol = 10^-5 ;
val = rand ;
A = rand(1,10) ;
A(5) = val ; % replace this index with vl to seek later
idx = abs(A-val)<=tol ; % logical indices
id = find(idx) % index
  1 Comment
Jonathan Moorman
Jonathan Moorman on 20 Aug 2020
Worked great!. Thank you

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